Process for the manufacture of fuel briquettes



PROCESS FOR THE MANUFACTURE O FUEL BRIQUE'I'IES Heinrich Dohmen, Deventer, Netherlands, assignor to N. V. Briko, The Hague, Netherlands, a company of the Netherlands No Drawing. Application September 10, 1956 Serial No. 608,683

Claims priority, application Netherlands September 13, 1955 11 Claims. (Cl. 44-24) According to the invention fuel briquettes are manufactured by treating coal, with the exception of lignite, with a small amount of an organic acid, mixing the thus formed product, if desired, with a solid fuel in divided form, and pressing this mixture, or the above-described product alone, at elevated temperature to a briquette.

Coal, after treatment with an organic acid, can be pressed to a briquette in the manner usual per se for briquetting, i.e. at an elevated temperature and under a short high pressure. When the treatment with acid is omitted, the capacity to be pressed to a briquette is absent, as is generally known, and coal therefore has always been briquetted with the aid of an additional admixed binding agent, such as pitch.

It is clear that for briquetting the organic acid cannot be considered as a binding agent in the usual sense. It seems, rather, that under the influence of the added organic acid, an adhesive force develops under the briquetting conditions which makes the treated coal (to which, if desired, an amount of non-treated coal can be added) pass to a solid briquette.

So far no sufiicient explanation has been given for the above described phenomenon. It is possible that the organic acid activates the bitumen present in the coal, owing to which the bitumen develops an adhesive force which binds the material. Another explanation could be based on the observation that the adhesive force developed is dependent on the ash content of the coal used, the adhesive force increasing with the ash content. Since these explanations at most point in a certain direction, they should not be conceived in such a manner that any limitation of the invention could be a result thereof.

Important is the particle size of the treated coal; the smaller the average particle size, the more solid is the briquette obtained. Therefore, it is undesirable for particles larger than approximately 3 mm. to be present in large amounts in the coal to be treated. The best results are obtained when the starting material is ground to a powder with an average particle size of approximately 0.1-0.2 mm.

The organic acid may be added to the coal after grinding. If desired, coal sludge, which has been obtained as a by-product from any stage of the recovery of coal, may be used as the starting material. Finally, the organic acid may also be added to the coarse starting material, and the latter may be ground thereupon, in which case there is an advantage that the organic acid can act on the freshly formed surface, the absorption capacity of which is greatest.

The treatment of the coal with the organic acid can be carried out at ordinary temperature, or during or after the aforesaid treatment of the coal. The acid can be added in finely divided condition or in liquid form, e.g. it can be sprayed over the coal in more or less finely divided form or applied in the form of a solution. Volatile organic acids can also be contacted with the coal in gaseous form.

Patented Jan. 26, 1960 When the coal is heated, it is brought to a temperature of preferably 80100 C. When organic acids, the boiling point of which exceeds 120 C. are used, a temperature above the said temperature range is preferred.

It has been found that acetic acid in a concentrated aqueous solution is very suitable for the treatment of the coal. Acetic acid, e.g. in a concentration of approximately 80%, can be used, and, dependent on the kind of coal used, the optimum amount of 80% acetic acid added varies from approximately 10 to approximately 30 cc. per kilogram of coal.

As noted above coal obtains the capacity to be pressed to a briquette by the treatment with the organic acid. The adhesive force. developed appears to be such that a larger or smaller amount of a non-treated solid fuel can be incorporated in the treated coal. The invention, consequently, inter alia, gives a solution for the problem of the use of large amounts of coal sludge which is formed in considerable quantities in any plant for the recovery of coal and which previously could not be worked up without the binding agent, pitch. It is an important characterizing feature of the invention that as the solid fuel which is bound With the aid of the coal treated with the organic acid, finely divided coal is used. The coal may be present in finely divided form, such as in the form of coal sludge, and the coal can be of any character from young bitumen-containing coal up to anthracite. It, consequently, is possible with the aid of the invention to manufacture a briquette, the binding agent of which consists of a coal which has been treated with the organic acid,-and the part to be bound of which consists of a coal which has not been subjected to the treatment with the organic acid. It will be clear that a minimum amount of the coal treated Withthe organic acid is used in the total amount of coal; and dependent on the kind of the coal used and on the character of the used pit coal, this minimum lies between a value of approximately 2 and approximately 4 parts by weight of the treated coal to approximately 98-96 parts by weight of pit coal.

In most cases the coal treated according to the present process contains more or less water before the treatment. This water can be removed entirely or partially by heating, drying with a dry flow of air or in any other manner. Also a small amount of a water-repelling agent, such as solid or liquid parafiin, can be added to the coal before briquetting.

The invention'is elucidated by the following examples.

Example 1 1000 g. of open burning coal (splint coal) were ground to a powder with an average particle size of approximately 0.15 mm., whereupon they were heated to 100 C. and

were sprayed in warm condition With 22 cc. of 80% acetic acid solution. The sprayed mass was well mixed and after mixing was immediately supplied to a briquetting machine of the usual construction. A solid, rapidly hardening briquette, the mechanical strength of which is at least equal to that of pitch briquettes, was obtained. Said briquette lies well in the fire and does not disintegrate on poking; its combustion is complete with a strong develpoment of heat.

1000 g. of the same open-burning coal were treated at C. with 20 cc. of formic acid. The treatment for the rest was the same, and the briquette obtained was hard, lay well in the fire and was poking-resistant.

In both above-mentioned cases 25 g. of solid or liquid paraflin can be added per 1000 g. of coal.

Example 2 whereupon. they were heated at, C. and were sprayed in warm condition with 20 cc. of 80% acetic acid solution.

The sprayed mass was well mixed and thereupon added to 2000 g. of ess-fine (semi-bituminous fine) which had been brought beforehand to a moisture content of 2%, and the mixture was heated to a temperature of 90 C. After the treated and untreated coal were well mixed, the mixture was pressed to briquettes. A hard briquette was obtained. Said briquette is resistant to weather and lies well in the fire. The mechanical properties were better than those of the usual pitch briquettes.

Instead of the acetic acid a 90% aqueous formic acid solution can be used.

Exam ple 3 300 g. of fat-fine, i.e. fines or sludge of fat coal, were ground to a powder with a particle size of approximately 0.2 mm.; this powder was heated to 90C. and treated with 6 cc. of 80% acetic acid. Moreover 50 g. of potato starch were brought at 70 C. and treated with 1.5 cc. of 80% acetic acid. These products wereintimately mixed and 8.75 g. of solid parafiin were added. The mixture thus formed was intimately mixed with 6000 g. of open-burning coal which had previously been heated to 60 C.; thereupon briquetting took place in a usual briquetting machine. The briquettes obtained satisfied the requirements satisfied by pitch briquettes, but missed the disadvantages adhering to the use of pitch; they were soon hard; they could withstand a fall from the prescribed height, were resistant to weather and water and gave full satisfaction in the burning test.

Example 4 1000 g. of open-burning coal with 32% of volatile matter were ground and treated, during heating'at 80 C., with 20 cc. of 80% aqueous acetic acid. The average particle size of the powder was approximately 0.15 mm. To this mixture were added 100 g. of lignite which had been treated with 10 cc. of 80% acetic acid at a temperature which during the addition of the acetic acid was gradually increased from 75 to 115 C. This mixture was immediately pressed to briquettes. The briquettes obtained satisfied all requirements made with respect to mechanical properties, the resistancy to water and weather, and the properties on the fire.

The above-described mixture (1100 g.) was used as a binding agent for an equal amount of dry burning coal fine. The properties of the briquettes obtained again satisfied all requirements which usually are made on fuel briquettes.

Example 5 1000 g. of semi-bituminous coal with 15% of volatile matter were ground to a powder with an average particle size of approximately 0.1 mm. and were mixed with 100 g.

of potato starch and 350 g. to lignite, and this mixture was heated at 100 C., whereupon 46 cc. of 80% aqueous acetic acid solution were sprayed over the mixture while this was agitated.

18 kg. of dry-burning coal fine with an average particle size of 2.5 mm. with a maximum of approximately 4 mm. were intimately mixed with the above-described mixture and immediately thereupon supplied to the briquetting machine. The briquettes obtained were hard and had a glossy surface; and when struck together, they gave a clear sound, were resistant to weather and water, and their solidity in the fire was also very good.

The treatment could also be carried out with a 90% aqueous formic acid solution at a temperature of 75 C. It was also possible to treat the coal, the potato starch and the lignite separately with the acid, or to combine the treatment of two of the startingmaterials and to treat the third separately.

. Example 6 1000 g. or at fine vei'atint 'zsa an an average particle size of approximately 1.0 mm., 5 g. of potato starch, 100 g. of lignite and 28 g. of solid paraffin wax were mixed and heated at C., whereupon 25 cc. of 80% aqueous acetic acid solution were sprayed over the mixture, while this was agitated. Immediately after the addition of-the acetic acid the mixture was supplied to the briquetting press; the briquettes obtained were hard and glossy, and well resistant to weather and water.

Example 7 kg. of anthracite-fine (particle size smaller than 0.1 mm.) with a moisture content of 6% (ash content 8%, 7.5% of volatile matter and without coking capacity) were heated at 45-50 C., and 20 cc. of 80% acetic acid per kilogram of anthracite were sprayed thereon. 4 kg. of solid p-arafiin wax were added in molten and finely divided condition, whereupon the mixture was briquetted at approximately 50 C. Hard briquettes were obtained which lay well in the fire and were resistant to weather and water.

Example 8 10 kg. of anthracite fine, of the quality as described in the preceding example and with the same moisture content, were heated at approximately 50 C., and 2.5 cc. to 80% acetic acid were added by spraying, while the coal was agitated. 10 kg. of potato starch were also heated at 50 C., and 7.5 cc. of 80% acetic acid were added.

Both conversion products were mixed with each other, and 4 kg. of parafiin wax were added in the same manner as in Example 7, whereupon 50 kg. of anthracite fine of the same quality as described above were added to the mixture and mixed therewith.

The mixture thus obtained was added to 1100 kg. of anthracite fine with the above-described properties, and after intimate mixing the mixture was briquetted. The moisture content and the temperature of the non-treated anthracite-fine were the same as those of the treated anthracite-fine.

The briquettes thus obtained were hard and lay well in the fire; they were weather and water resistant.

Example 9 The same binding agent as in the preceding example was prepared, but instead of anthracite-fine with a moisture content of 6%, 1100 kg. of anthracite-fine with a moisture content of 1 0% were briquetted. The briquettes obtained did not harden less rapidly than those of the preceding example, and also the further properties of the briquettes were unchanged.

Example 10 100 'kg. of fat coal (ash' content 9.2%, content of volatile matter 24.5%, baking capacity 11) with a moisture content of 8% and a particle size up to 0.1 mm. were mixed at 60 C. with 4 kg. of paraflin wax and 2 liters of 80% acetic acid and pressed to briquettes at the same temperature.

The briquettes were hard and glossy practically immediately; they lay well in the fire and were weather and watelr resistant.

Example 11 1 kg. of fat coal of the same properties and with the same moisture content as in the preceding example was treated with 2.5 cc. of 80% acetic acid.

1 kg. of potato starch was treated with 7.5 cc. of 80% acetic acid and the fat coal, the potato starch and 40 g. of molten parafiin wax were intimately mixed with each other while heating at a temperature up to 50 C. To the mixture thus obtained 5 kg. of fat coal fine of the same composition as above were added until a homogeneous mixture had been formed, and thereupon another kg. 'of fat coal were added and the whole was pressed to briquettes at 50 C. after mixing. The

briquettes thus obtained were hard very soon, lay well' in the fire and were weather and water resistant.

Example 12 100 kg. of semi bituminous coal (ash content 8.5%, content of volatile matter 14.8% and baking capacity 4 to 5) with a particle size up to 4 mm. and a moisture content of 8% were mixed with 4 kg. of molten solid parafiin wax and 2 liters of 80% acetic acid while heating at 50 C. The mixture was briquetted at the same temperature. The briquettes thus obtained were hard, they lay well in the fire and were resistant to weather and water.

Example 13 1 kg. of semi bituminous coal with the same properties as described in the preceding example was treated at 45 C. with 2.5 cc. of 80% acetic acid, and 1 kg. of potato starch was treated at the same temperature with 7.5 cc. of 80% acetic acid. The treated coal and the treated potato starch were mixed with 5 kg. of semibituminous coal with the same properties as the starting material and thereupon this mixture was mixed at 45 C. with 110 kg. of untreated semi-bituminous coal while adding 4 kg. of molten paraifin, and briquetted.

The briquettes were hard and glossy, resistant to weather and water, and lay well in the fire.

Example 14 kg. of anthracite of the quality described in the Examples 7-9 were treated with 200 g. of potato starch without addition of acetic acid at 50 C. and the mixture thus obtained was passed through the briquetting machine. Owing to the absence of the organic acid, whereby the mixture had no binding capacity, no briquettes were obtained, but lumps without cohesion were formed which when the slightest pressure was applied disintegrated to powder.

What is claimed is:

1. A process for the manufacture of fuel briquettes comprising mixing coal selected from the group consisting of bituminous and anthracite coals, the particle size of which is essentially less than about 3 mm., with from 10 to 30 cc. of concentrated lower aliphatic monocarboxylic acid selected from the group consisting of acetic acid and formic acid per kilogram of coal and briquetting the product.

2. A process according to claim 1 in which the coal is in the form of a powder having an average particle size of from 0.1 to 0.2 mm.

3. A process according to claim 1 wherein the mixing 6 is carried out at a temperature between about and 4. A process according to claim 1 wherein the lower aliphatic carboxylic acid is acetic acid having a concentration of 80%.

5. A process for the manufacture of fuel briquettes comprising mixing coal selected from the group consisting of bituminous and anthracite coals, the particle size of which is essentially less than about 3 mm., with from 10 to 30 cc. of concentrated lower aliphatic m0nocarboxylic acid selected from the group consisting of acetic acid and formic acid per kilogram of coal, mixing the resulting product with solid fuel in divided form and briquetting the mixture.

6. A process according to claim 5 in which the coal is in the form of a powder having an average particle size of from 0.1 to 0.2 mm.

7. A process according to claim 5 wherein the lower aliphatic carboxylic acid is acetic acid having a concentration of 80%.

8. A process according to claim 5 wherein the solid fuel is finely divided pit coal.

9. A process according to claim 5 wherein the solid fuel is coal sludge.

10. A process according to claim 8 wherein at least about 2 to 4 parts by weight of the mixture of coal and acid are mixed with at most about 98 to 96 parts by weight of the pit coal.

11. A process for the manufacture of fuel briquettes comprising reacting coal selected from the group consisting of bituminous and anthracite coals, the particle size of which is essentially less than about 3 mm., with from 10 to 30 cc. of concentrated lower aliphatic monocarboxylic acid selected from the group consisting of acetic acid and formic acid per kilogram of coal, mixing paraffin wax with the resulting product and briquetting said mixture.

References Cited in the file of this patent UNITED STATES PATENTS 726,029 Classen Apr. 21, 1903 793,771 Dallas July 4, 1905 1,050,535 Hartung Jan. 14, 1913 2,448,605 Kleinicke Sept. 7, 1948 FOREIGN PATENTS 27,960 Great Britain Sept. 8, 1910 568,280 Great Britain Mar. 27, 1945 

1. A PROCESS FOR THE MANUFACTURE OF FUEL BRIQUETTES COMPRISING MIXING COAL SELECTED FROM THE GROUP CONSISTING OF BITUMINOUS AND ANTHRACITE COALS, THE PARTICLE SIZE OF WHICH IS ESSENTIALLY LESS THAN ABOUT 3 MM., WITH FROM 10 TO 30 CC. OF CONCENTRATED LOWER ALIPHATIC MONOCARBOXYLIC ACID SELECTED FROM THE GROUP CONSISTING OF ACETIC ACID AND FORMIC ACID PER KILOGRAM OF COAL AND BRIQUETTING THE PRODUCT. 